Advanced Materials Research Vols. 391-392

Abstract: Finely dispersed Al-doped ZnO (AZO) nanoparticles with well crystallization were prepared by a modified sol-gel combustion synthesis. The AZO nanoparticles with different Al doping concentration were calcined at 600 °C. In order to investigate the physical properties and microstructural characteristics, the nanoparticles were characterized by bulk density measurement, scanning electron microscope (SEM) and X-ray diffraction (XRD). The XRD patterns of AZO nanoparticles corresponded well to the hexagonal structure of ZnO, indicating that the partial Zn atoms were substituted by Al atoms. With the increase of Al doping concentration, the size of AZO nanoparticles decreased from 30.43 nm to 25.97 nm. Simultaneously, with changing the atom ratio of Al/Zn, the bulk density varied obviously.

Abstract: The citric-acid coated Mn-Zn ferrite nanocrystalline was prepared by an improved co-precipitation method. X-ray diffraction (XRD) and TEM measurements indicated that the coated samples were pure spinel Mn-Zn ferrite nanocrystalline and the particles coated after boiling circumfluence were more homogeneous than that before boiling circumfluence. Vibrating sample magnetometer (VSM) indicated that the Ms of the coated samples was higher than that without coating. Specially when the content of citric acid is 4.76wt% after boiling circumfluence, the Ms of the coated sample is 54.15 emu•g^-1 which is 28.7% higher than that without coating.

Abstract: Mn_0.49Zn_0.48Fe_2.06O₄ ferrite nano-powders were prepared by co-precipitation method and pressed into ring samples by dry pressing to study the effect of sintering atmosphere, sintering temperature and heating rate on properties of Mn-Zn Ferrites. X ray diffraction (XRD), scanning electron microscopy (SEM), and vibration sample magnetometer (VSM) were used to characterize properties of the obtained samples. It was shown that the samples sintered in nitrogen contained no impurities with cubic spinel structure. The samples sintered at 880°C with heating rate of 5°C/min had a density of 4.82 g•cm^-3, high quality factor Q of 57 at a frequency of 2MHz, high saturation magnetization Ms of 90.02emu•g^-1.

Abstract: In the laboratory condition, a series of experiments were carried out in a sintering pot in order to improve the tumbler strength of low SiO₂ sinter. The results shows that the content of SiO₂ is decreased from 4.4wt% to 3.9wt% when the ratio of serpentine is decreased from 2.2wt% to 1.0wt%, as a result, the tumbler strength and the reduction degradation index of sinter all fall down. When the ratio of serpentine is further decreased, all kinds of sintering indexes fall down rapidly. If the basicity of sinter is increased from 1.75 to 1.85, and 5wt% iron concentrate is added in sintering mixture, the content of SiO₂ can be decreased to 3.9wt%~4.0wt%, meanwhile, the tumbler strength of sinter is the same as that of the reference sinter with 4.4wt% SiO₂. When Niuman iron ore, Hainan iron ore and Hamosili iron ore are used as the hearth layer instead of sinter, and the basicity of sinter is increased to 1.85, the tumbler strength of sinter with 3.9wt%~4.0wt%SiO₂ is the same as that of the reference sinter with 4.4wt% SiO₂.

Abstract: In order to evaluate the thermal cracking resistance of shotcrete under the condition of practical temperature field and strong restrain, a proper test method is needed. Based on temperature matched curing and by applying temperature stress testing machine, a new test method has been provided. With the application of this test method, thermal cracking resistance of three shotcretes with different types of fiber were investigated. Test results show that the cracking tendency of different shotcretes can be distinguished with the parameter of the difference between the max temperature and the cracking temperature.

Abstract: This paper studies the effect of metakaolin mixed with fly ash on the compressive strength of concretes. The results show that in order to improve the property and reduce the price of metakaolin, metakaolin can be used with fly ash together, and the optimal content of metakaolin in concrete is not bigger than 10%. The content of metakaolin affects the early compressive strength of fly ash concrete significantly. When the water-bind ratio is 0.31 and the amount of metakaolin and fly ash is 35%, which the metakaolin content is 8%, the compressive strength can increase up to 54MPa; when the mixed additive and metakaolin are 25% and 8%, the compressive strength reaches 68MPa.

Abstract: In this paper, a kind of nano ATO heat-insulation glass coating was prepared by using silicone emulsion and nano tin dioxide (ATO) powder with ethanol as solvent. The properties of glass coating, such as transmittance, as well as thermal and mechanical properties, and the optimization of the ATO level were discussed. The results showed that this glass coating had good transmittance of visible light and good heat-insulation performance. The transmittance of visible light was above 75% and the highest temperature difference between the heat insulating and ordinary glass is 17°C. It had good energy-saving effect and could be widely used as architecture glass and automobile glass coating.

Abstract: The changes of structure and mechanical properties of poly(p-phenylene benzobisoxazole) (PBO) fibers with different heat-treatment condition involving temperature, level of tension and duration was investigated. The results revealed that the modulus of fibers was affected greatly by the heat treatment, while the strength of fiber was insensitive to the applied parameter during the heat treatment. It was also found that the heat treatment could promote the ring-close reaction of PBO molecules to completion and impelled the molecular chains to adjust and slide along the stress direction for further orientation, which could make the molecular chain more stretched, regularize the structure of PBO fibers and improve the mechanical properties of PBO fiber.

Abstract: HIPIB irradiation into AZ31 magnesium alloy is performed at ion current density of 100-300 A/cm² with 1 shot. The surface morphologies and surface profiles of the irradiated AZ31 magnesium alloy samples are characterized by scanning electron microscopy (SEM) and profilometer, respectively. It is found that HIPIB irradiation leads to the formation of crater in local region of irradiated samples, and crater density increases with increasing ion current density. Both the surface roughness that reflects the vertical wave of surface profile and the mean spacing of surface profile irregularities that reflects the horizontal wave of surface profile increase as ion current density increases. These results are in agreement with the SEM observation on the irradiated surface.

Abstract: The effects of calcium salts of aliphatic dicarboxylic acids on the polymorphism of iPP have been investigated by means of WAXD, DSC and PLM. It is found that β crystalline form content and nucleation ability of the nucleated iPP are dependent on the carboatomic numbers of the acids. Calcium salts of malonic acid, glutaric acid, pimelic acid and suberic acid are good β nucleators. Calcium salts of succinic acid and adipic acid are α nucleators. Calcium salts of acids with carboatomic numbers of 5 to 8 are good nucleators. The β spherulite size is the smallest in iPP doped with calcium pimelate.